It was a massive mistake because people can now see Trump and Biden's speeches side by side in the same day. People might not like Trump, but public speaking is one of his strongest traits, and one of Biden's weakest.

If you watch Trump you'll see him read his notes and speak his mind for an hour or two. It sounds natural and genuine and it can be entertaining. Imagine going from that to one of Biden's five minute videos of him staring hollowly at a teleprompter and still fucking it up. That's a rough transition which won't sit well with a lot of people.

But now Biden is basically locked into it. If he quits he looks weak and Trump can call him out, and if he keeps going he will keep looking like an idiot. Biden and the people running his campaign really don't know what they're doing.